Cutting tool



June 19, 1951 J. B-ARM|TAGE ET AL 2,557,404

CUTTING TOOL Filed May 9', 1945 2 Sheets-Sheet 1 f/VVEN T025 SEP/Y E A2M/'TAGE ALFRED Q Sam/ffm' June 19, 1951 J. B. ARMITAGE YE1' Al.

' CUTTING TooL 2 Sheets-Sheet 2 Filed May 9, 1945 JNVENTORS JasEPH 5 m1171465 HL2-25p dv JFK/um? *3y 7 l 14 :'Toemgy Patented June 19, 1951 CUTTING TOQL Joseph B. Armitage and Alfred 0. Schmidt, Wauwatosa, Wis., assignors to Kearney & Trecker Corporation, West Allis, Wis., a corporation of Wisconsin Application May 9, 1945 Serial No. 592,826

8 Claims. (Cl. 252-105) This invention relates to cutting tools for man chine tools and more particularly to cutter tooth construction.

A general object of this invention is to provide a machine tool cutter having teeth with dual tooth faces.

Another object of this invention is to provide a cutter having the combined advantages of conventional positive and negative rake angle cutters.

A further object of the invention is to provide a cutter tooth having a primary rake angle to increase the strength of the cutting tip yand a secondary rake angle to reduce the power required to operate the cutter.

A further object is to provide a multiple tooth cutter having improved chip ilute construction provide a continuous and even ow of chips` A still further object of the invention is to provide an improved blade clamping mea-ns for an `inserted blade type cutter, in order to leave the front side of the blade clear for chip control.

Another object of this invention is to provide a general purpose cutter which may be readily converted from a negative rake cutter to a positive rake cutter or vice versa.

A further object vis to provide a dual `faced cutter blade requiring a minimum of stock to be removed to renew the cutting edge and thereby conserve cutter tip material.

Ano-ther object is to provide a cutter tooth formation in which the tendency to crater vis minimized.

Another object is to Yprovide a dual faced cutprimary tooth face can `be readily changed from positive to negative or from negative to positive without resetting the blades or altering the cut.- ter body. In addition, the cutter body chip flute is designed to guide the chip away from the cutH ting edge with extreme ease with the blade clamping means disposed behind the blade.

The foregoing and other objects and advantages of this invention will become apparent from the 4following specification and may be achieved by the cutting tool described in connection with the accompanying drawing illustrating the in.` vention, in which:

Figure 1 is an elevational view showing a .cutter, incorporating the principles of the invention, operating upon a workpiece;

Fig. 2 is a bottom view of the cutter shown in Fig. l, showing the cutting blades clamped in po.- sition;

Fig. 3 is a transverse section on the 1in 3-3 in Fig. 2, showing the position of the blade and wedge in a cutterslot;

Fig. 4 is a diagrammatic showing of a conventional negative Vradial vrake and a positive radial rake cutter tooth;

Fig. 5 is an enlarged view -of one of the lcutter blades shown in Fig. 2 with the cutter tip construction exaggerated to fully disclose the invention;

Fig. 6 is a modication of the invention, as shown in Fig. 5, showing a double face cutter tooth;

Fig. 7 is an elevational view of a cutter in which the dual faced blades are mounted at a negative axial rake angle;

ter` which may be readily sharpened by grinding a minimum of stock from one of the tooth faces Fig. 8 is an enlarged view of a cutter blade disand the land behind the cutting edge. posed at a negative radial rake showing crater- According to this invention, as improved multiing action thereon;

y ple tooth cutter is provided for use with a ma* Fig. 9 is an enlarged view of a conventional chine tool wherein the cutter teeth are designed negative rake cutter blade with dotted `lines sugto provide Vmaximum cutting eiciency with a gesting the amount of stock removed in sharpen-'- minimum of power expended. The cutter is proing the blade; and vided with teeth having aprimaryrake angle and Fig. 10 is an enlarged view of the improved a secondary rake angle. 'The primary angle is cutter blade with dotted `lines suggesting the chosen to provide the greatest strength at the `4:5 amount of stock removed in sharpening this type tip of the tooth while the secondary angle is seof blade. `leeted to reduce deformation 4in the chip and, Referring to Fig. 1, a cutter Il) is rotatably CODSSQUCHLY, 150 leqllle a minimum 0f Operating driven by Aa tool retaining spindle I l in a machine power from the machine tool lper unit ofcutting tool and is disposed to engage a workpiece l2 -force expended. Cratering and excessive wear clamped on a reciprocal tube I3 of the said tool. on the tooth faces is reduced considerably. As is usual in milling machine practice, provision When resh-arpening the cutter, a light cut off 0I is made to drive the cutter at any one of a pluthe primary face and Ithe relief iace behind the rality of speeds within a comparatively wide edge serves to renew the cutting `edge and to Yrange and to operate the workholder or table at conserveV the ytip stock. The rake ang-1e -of the 55 @De 0f a plurality 0f feed ratei Although the drawing shows the cutter incorporating the invention applied to a milling machine, it is to be understood that the invention may be readily adapted to other types of machine tool cutters with equal advantage. The cutter is assumed to be rotating in the same direction, as indicated by the arrow in each of the figures.

The cutter assembly I0, as shown in Figs. 2 and 1, is of the face mill type and comprises a cutter body I5 having a plurality of cutter blades or teeth I6 disposed in machined slots I1 therein. Each blade is rigidly clamped in the body by a wedge plate I8, which is locked in position by a self-locking cap screw I9. The machined slot I1 has parallel side walls, while mating surfaces 20 on'the blade and wedge are inclined at a slight angle relative to the side walls, as shown in Fig. 3. With the parts thus disposed in the slot, the wedge I8 may be driven into a blade locking position with sufcient force to retain the blade I6 against all movement, including endwise movement. The screw I9 is used as a safety measure, although tests have shown that the blades will not loosen when retained in this manner with the screw omitted.

The development of machine tool cutters in the past has been more or less a matter of chance. However, recent technological advances 'in the machine tool field have necessitated a complete change to a strictly scientific basis of development. The various angles on the cutter blade or tooth are important in determining the efliciency of the cutter. Each combination of angles serves to produce a different result in cutting. Thus, it was found that the radial rake angle of the blade, i. e., the angle formed between the blade face and a radial line passing through the blade nose or cutting edge, is vitally important. Most of the .early multiple tooth cutters were formed with the blade or tooth positioned at a positive rake angle, as shown by angle A in Fig. 4. The inherent weakness of this type of blade or tooth is that the lip angle, as designated by the angle B, is comparatively small and, consequently, the blade is weakest structurally directly behind cutting edge 22. Although the tool forces are less for cutters with this type of blade, this weakness will cause the cutting edge to wear and the power requirements of the cutter will rise quickly as the edge break down from such wear. Y

A second type of multiple tooth cutter uses a negative rake angle blade or tooth. This type of blade is shown in Figs. 4, 8 and 9 with the negative rake angle, i. e., the angle between a s.,

edge 22, since more stock lies behind this edge.

The lip angle, as designated by the letter D, is greater than the lip angle B of the positive rake cutter blade. This causes the tool forces to lbe higher in the negative rake angle cutter but, since Wear occurs on the cutting edge at a slower rate, the power requirements of this cutter will increase more slowly than the power requirements of a positive radialvrake cutter as the edge wears. The tooth faces on this type of cutter tend to crater, as suggested by lines 24 in Fig. 8, due to the excessive friction created by the chips during a cutting operation.

By using double radial rake angle cutter blades or teeth according to the teaching of this invention, as shown in Figs. 5 and 10 and hereinafter fully described, the advantages of both positive radial rake and negative radial rake cutters are obtained. A primary tooth face 21 is disposed immediately adjacent to the cutting edge 22 while a secondary tooth face 28 adjoins the primary tooth face. These two faces constitute the leading face of a cutter tooth or, in the case of an inserted type cutter, they constitute the leading face of a cutter blade. The primary face 21 is disposed at an angle C to the radial line 23 extending through cutting edge 22 of the tooth or blade and the secondary face 28 is disposed at an angle A to the radial line. Actual tests have shown that, for milling steel, the angle C should preferably be a negative rake angle in the range of 0 to 15, while the angle .A should be in the range of 0 to 30 positive. In Figs. 5 and 10, a primary rake angle of 15 negative was used and a secondary rake angle of 30 positive was used. It is to be understood that the values accorded these angles were chosen for illustrative purposes only and that the actual values accorded them should be determined from numerous tests based on such factors as cutter design, material in the cutter, and the material in the workpiece upon which the cutter is operating.

Cutting forces are imparted to the blade at right angles to the tooth face. Thus, as shown in Fig. 4, the cutting forces acting upon the blade I8 disposed at a positive radial rake angle would necessarily act in a plane through the tooth tip parallel to the cutting edge 22, as suggested by an arrow 29. Since the amount of stock along the cuting edge is very small, the cutting forces naturally tend to shear off the edge at the time of impact with the workpiece. In the case of a negatively disposed cutter blade, the cutting forces imparted to the blade during a cutting operation are counteracted by a tooth force substantially greater than that occurring in a blade disposed at a positive radial rake angle. In this type of blade, the amount of stock available to counteract the cutting forces imparted to the tooth face is generally equal to the width of the cutter blade. In the case of a cutter blade or tooth having a double rake angle tooth face, such as is shown in Fig. 5, the amount of stock directly behind the primary tooth face 21 is substantially greater than the amount of stock in a corresponding plane in either the conventional positive or negative rake angle blades, such as are shown in Fig. 4. Thus, a cutting force imparted to the primary tooth face 21, as suggested by an arrow 30 in Fig. 5, would be imparted to the blade or tooth at right angles to the primary face. The amount of stock in a plane substantially at the center of the primary tooth face 21 is indicated by an arrow 3| and an arrow 32. The arrow 3l represents the maximum width of stock in a similar plane in a negatively disposed cutter blade, as suggested by the dotted line showing in Fig. 5. Since the amount of stock, indicated by arrow 3 I, in a plane substantially at right angles to the tooth face of a negatively disposed cutter blade represents the maximum amount of stock available to counteract the cutting forces because of the cutter or tooth design prior to this time, the gain in stock, as represented by the arrow 32, is rather substantial. This improved tooth design has resulted in a great increase in cutter life. The heat created by the contact of the cutter tip with the workpiece while the blade is moving through the metal will be more readily dissipated because Of the greater cross sectional area in this type .of blade and, consequently, the cutting `edge 22 will stand up far better during aproduction xcutting operation :than would the :conventional `positive or negative rake type of cutter.

Since the power requirements of :a negative `rake cutter are substantially higher than a positive rake cutter, the length of the primary tooth :face r2.1 is held to va minimum. The optimum length may be readily 4determined .by various tests.

Thus, for 'steel 4cutting operations, it has been found that the length of the prima-ry tooth face, as indicated by the arrow '33 .should be' approximately .one to three times the width vof -feed per tooth, which will be taken with the particular cutter; while in the case of .cast iron cutting operations, it need only "oe :one-half of .the 4width of toed per tooth. The secondary tooth face 28 ad- .ioining the primary face is disposed to gain the inherent advantage of a positive radial rake cutter, namely to require a minimum of power during 4.the cutter operation by aiding the ilow vof chips away from the cutting ledge v22.

'The cratering on a negatively `disposed blade or tooth occurs on the tooth face .somewhat away from the vcutting edge. superimposed on the negatively .disposed blade, vas suggested by dotted lines in Fig. 8, it `will be .readily .seen that the length .of the primary .face 21 corresponds .approxi-mately .to the distance v.from the :cutting edge 22 to the ,point at which the .crater 24 begins to form. .Since .cratering is caused by `the .extreme pressure of the .chips upon the tooth face and is especially pronounced on a negatively ydisposed blade .or tooth vafter the cutter has been used awhile, it is evident that v.the .cratering .action can be reduced .or eliminated 'by reducing the negative rake angle or preferably by using a positive rake angle .A such as is .used with .the secondary tooth face 2.8, This .face is well behind the crater 2-4 and, consequently, little or no cratering will .occur thereon. .As the chips leave the primary face 21 the pressure between the chip and the toothface is .gradually relieved as it moves across the .secondary tooth face 28. The chips may or may not .actually engage the face 2.8 depending on the rake .angle used and upon the thickness of the chips.

In the inserted blade type of cutter, the angle of .the secondary tooth ace ..28 .is determined by the rake position of the blade I 6 in the cutter body l5 while the primary tooth .face 21 is actually ground on the tip of the blade. In a solid .cutter with v.teeth integrally formed with the body, the primary tooth is precision ground., while the secondary face is formed in the cutter 'body and, if accurately formed Originally, may never need regrinding. Likewise., .in the case of cutters having brazed tips, the secondary angle corresponds to the Iangle at which the tip is brazed on .the body, while the primary tooth face Vis `formed identically on all of theteeth by a simple precision grinding operation.

Sharpening cutters having .a double tooth face is .comparatively simple, since it is generally sufficient to regrind only .the primary tooth faceand the landular surface behind .the cutting edge.. A few thousandths f .an inch of stock removed .from each of these surfaces is generally sucient to remove any craters or worn spots and .to present van entirely new pair .of surfaces and a new :cutting edge. As suggested by dotted lines 34 in Figs. and 10, the total amount of material re moved in sharpening this type of tooth .is very nominal .in comparison with the amount of .material removed when sharpening .conventional type If .a dual `faced blade is cutters having .a single rake angle. In these types of cutters, cratering .occurs-.on the :tooth .face immediately adjacent to the cutting .edge .and excessive vwear generally .occurs .on both faces adjacent to the edge. In order to remove 'the craters on the tooth vface and the worn surfaces. itis necessary to grind a considerable amount of .stock from the entire end of the blade whenever the cutter is sharpened. Thus, as in the Jcase of a blade set 'at a negative radial rake angle vC having a crater 24 worn in the tooth face, as shown in Fig. 9, the cutting edge 22 could be renewed only .by taking .a .cut 01T .of the entire top end yof the blade. After five sharpenings, as suggested by the .ve dotted lines 31, the blade would .have to vbe reset in the cutter body 1 5, or whereas, in the case of .a brazed carbide tipped blade., `the blade would have to be scrapped. In sharpening a dual faced blade five times, as suggested by the dotted lines in Fig. 10, very little .stock is removed. The expensive carbide steel tip stock is conserved .in this manner. Thus, it is evident that the `overall life of a double faced type cutter is much longer, since the cubical capacity of the .material removed with this cutter is much greater between resharpenings and the amount .of stock necessarily removed to re- ;sharpen the cutter is much less.

A mozdication in the blade tip or tooth structure of a acutter'incorporating a multiple tooth face with each having a rseparate rake angle is show-n in Fig. 6.. This modication in the `tip .structure is especially useful in cutters adapted to operate .on non-ferrous .metals such as aluminum and brass. .In this case, the cutting edge 22 is strengthened by providing a primary tooth face 21 set at a positive radial rake angle E. A .secondary tooth face 28 is disposed adjacent .to the primary face 21 at a positive radial rake angle A. Since angle E is smaller than angle A, the tip is strengthened suil'lciently to withstand the increased cutting forces incurred when cutting .such metals at an increased feed rate.

A general purpose cutter is provided in that the cutter may be readily converted from a positive to a negative rake angle cutter, or vice Versa, merely by regrinding the primary tooth face 21. In comparing the primary face formation in Figs. .5 .and 6 it is evident that very little stock would be lost in converting the'cutter. The blade would not have to ybe reset in the cutter body since 'the secondary rake angle A would remain the same. `rIhus, in a small shop only one cutter of 4a particular style would have to be carried in stock. In like manner, the angle of the primary face 21 may 'be readily changed to meet the requirements .of a particular cutting operation. In the conventional type of cutter, the rake angle is determined by lthe setting or position of the blade or tooth in the cutter body and, consequently, such a conversion is not possible.

With .the double face tooth, the chips are severed from the workpiece with a minimum of power expended. The primary face 21 serves to present a greatly strengthened .cutting edge to the work-piece in order to withstand cutting forces .suiiiciently great to deform the metal and .eiect sepa-ratioi-i in the cutting plane. The secondary y-face 28 ser-ves to afford la path offering a minimum of resistance to the chip as it leaves the primary face. An axially disposed chip control or guide means in the form of a flute 35 integrally formed in the cutter body l5 provides a .conftinuous :guide surface upon which the Ychip can slide from the secondary face 28, asindicated by an arrow 36 in Fig. 2.

. As previously described, the blade wedge plate I8 and lock screw I9 are located directly behind the blade I6 and do not present an obstruction to chip flow, such as often occurs in conventional cutters having the wedge plate in front of the blade. Thus, the curvature of the ute 35 can be sufliciently large and predeterminately formed to carry the chips off of the secondary face 28 with a minimum of interference. Due to the rotation of the cutter, an inertial force is imparted to the chip to throw it out of the cutter flute and leave the blade or tooth clear for a subsequent cut. The secondary tooth surface and the curved surface of the flute provide a continuous guide and support for the chip. All chips ejected from a cutter incorporating this feature are identically formed and do not show any signs of excessive deformation. Tests have shown that the elimination of such chip deformations results in a great reduction in the power demands on the machine tool utilizing the cutter, together with a reduction in vibration and machine maintenance. This feature is especially valuable in cutters which are to be operated at extremely high speeds.

In Fig. 7, the invention is shown applied to cutter blades I6 carried in a cutter body I5 at an axial rake angle F and having a peripheral cutting edge angle or corner angle G. The dual radial rake angles on this blade offer the same advantages as previously described. 'Ihe blades may be mounted in the body I in slots Il with the wedge f8 disposed behind the blade to lock each one in position. Thus the front of the blade is left open for chip control via a ilute 35.

While the invention has been shown and described vvith dual radial rake angles, it is to be understood that it may be applied with various combinations and types of rake angles with equal advantage. It is to be likewise understood that the angles shown in the drawing were chosen to best exemplify the invention and that the actual values which could be accorded such angles, or combination of angles, are very numerous. Rake angle values are dependent on various factors such as the type of cutter, type of material in the cutting tip, and the type of material being cut; and, consequently, can best be determined by operational tests.

Although the invention has been shown and described in considerable detail for the purpose of making a full disclosure thereof, it should be understood that the individual features of the invention may be included in other structural forms wtihout departing from the spirit and scope of the invention, as described in the subjoined claims.

The principles of the invention having now been fully explained in connection with the foregoing description of the illustrative embodying apparatus, the invention is hereby claimed as follows:

1. A high speed rotary cutter for machine tools, comprising a cutter body having a plurality of slots, a plurality of blades disposed in the slots, clamping means behind each of said blades, a cutting edge on each of said blades, a primary tooth face joining with said edge, a secondary tooth face adjacent to said primary face, a chip guide means joining with said secondary face whereby chips resulting from a cutting operation with said rotary cutter are carried away from said edge and primary face onto said secondary face `8 and said guide means at a high rate to positively clear said edge of chips.

2. In a multiple tooth rotary cutter for amachine tool, a cutter body, a plurality of teeth on Said body, a secondary tooth face on each tooth with a positive radial rake angle, a primary tooth face adjacent said secondary face on each tooth having a negative radial rake angle, a landular surface on each tooth, and a cutting edge formed at the junction of said landular surface and said primary face of each tooth whereby said cutting edge is strengthened by said primary face and chip ow is facilitated by said secondary face.

3. A multiple tooth rotary cutter for a machine tool and having a body and a plurality of radiating teeth, each tooth having a relief land, a primary tooth face, a cutting edge formed at the junction of said land and said face, a secondary tooth face adjoining said primary face, andral chip guide means meeting with said secondary face whereby said primary and secondary faces and said guide means provide a continuous guiding surface for chips.

4. A tooth formation for a machine tool cutter, comprising a cutter body, a plurality of evenly spaced teeth on said body, a cutting edge on each tooth, a primary tooth face adjacent each cutting edge at a negative radial rake angle to strengthen said edge, a secondary tooth face joining with said primary face at a positive radial rake angle to facilitate chip flowage from said cutting edge, and a chip control means in said body joining with said secondary face to eject chips from said cutter body.

5. In a machine tool cutter, a cutter body, a plurality of teeth projecting from said body, a land on each of said teeth, a primary tooth face on each of said teeth, a cutting edge formed at the junction of said land and said primary face, and a secondary tooth face adjacent said primary face, whereby said cutting edge may be renewed by grinding a minimum of stock from said land and said primary face.

6. A rotatable high speed cutter comprising a. cutter body, a plurality of teeth extending from said body, a cutting edge on each of said teeth, a primary tooth face adjacent each edge, a secondary tooth face joining with said primary face, a chip control means joining with said secondary face whereby chips during a cutting operation pass from said edge and said primary face onto said secondary face with diminished pressure and are continuously supported and guided by said face and said means until ejected from said cutter.

'7. A rotary machine tool cutter comprising a cutter body having a plurality of slots formed therein at a positive rake angle, a plurality of cutting blades clamped in the slots on said body, a cutting edge on the extreme forward end of each of said blades, a primary tooth face formed at a negative rake angle adjacent the cutting edge on each of said blades, a secondary tooth face joining with said primary face and formed by the angle of said blades in said cutter body. and a chip guide means predeterminately shaped and disposed in said cutter body adjacent said secondary tooth on said blades to receive chips therefrom in a manner to form them with a minimum of power being required to drive said cutter.

8. A multiple tooth cutter for machine tools comprising a cutterbody having a plurality of blade retaining slots formed in said body at a positive radial rake angle, a plurality of blades mounted in the slots of said cutter body and each presenting a cutting edge on the outermost end thereof, a primary tooth face on each tooth adjacent the cutting edge with said face formed thereon at a preselected negative rake angle, and a secondary tooth face adjoining said primary tooth face on each of said blades and having a positive radial rake angle corresponding to the radial rake angle of the slots in said body whereby the angle of said primary tooth face may be readily changed by grinding Without changing the position of said blades in said cutter body.

JOSEPH B. ARMITAGE. ALFRED O. SCHMIDT.

REFERENCES CITED The following references are of record in the le of this patent:

Number 15 Number 10 UNITED STATES PATENTS Name Date Miller Feb. 18, 1930 Klopstock Apr. 29, 1930 Swanson June 6, 1933 Binns July 3, 1934 Marshall Mar. 10, 1936 Kraus Jan. 9, 1940 Morse Apr. 29, 1941 Reaney Aug. 31, 1943 Kraus Jan. 16, 1945 Seiter Aug. 14, 1945 FOREIGN PATENTS Country Date Germany Oct. 27, 1939 

